Engine air/fuel feedback control systems are known in which a feedback variable derived from an exhaust gas oxygen sensor trims fuel flow to the engine in an effort to maintain desired air/fuel operation. Typically, the feedback variable is limited to fixed upper and lower limits thereby providing a range of authority for air/fuel feedback control. It is also known to provide an adaptively learned feedback correction term or variable derived from a difference between the feedback variable and its desired value. Such a system is disclosed in the U.S. Pat. No. 5,158,062.
The inventors herein have recognized numerous problems with the above approaches. One problem is that the range of authority of the feedback control system is defined by fixed limits of the feedback variable. Under certain operating conditions, wherein the feedback correction term has not reached its mature value, the feedback variable will be prematurely limited.